Process for producing aluminum oxanes, in particular methylaluminum oxane, from water and organoaluminum compounds, in particular trimethylaluminum, in inert hydrocarbons

ABSTRACT

A process is disclosed for producing aluminum oxane by subjecting frozen water in a solution of trialkylaluminum in hydrocarbons to erosive action. In particular, a process is disclosed for producing methylaluminum oxane which is characterized in that frozen water in a solution of trimethylaluminum in hydrocarbons is subjected to erosive action which is exerted by mechanical action or by one or more intensive liquid jets of the reaction solution sweeping over the surface of the frozen water.

Aluminum oxanes are formed during the controlled reaction of aluminumalkyls with water. A typical characteristic is the linking of twoaluminum atoms which still carry organic groups through an oxygen atom.The first representative of the aluminum oxanes isoxo-bis-dialkylaluminum or tetraalkyldialuminum oxide. Its isolation andcharacterization, particularly with methyl as the alkyl group, are notknown to this day.

As a rule, the reaction between water and aluminum alkyls results incomplete hydrolysis, in other words, in the formation of aluminum oxide,often with violent reaction and even flame formation.

A number of different methods have been developed for the cautious,controlled and incomplete reaction between water and aluminum alkyls.They have been published by (1) E. J. Vandenberg, J. Pol. Sci. 47 (1960)485; (2) N. N. Korneev, A. F. Popov, E. J. Larikov, A. F. Zhigach and G.B. Sakharovskaya, J. Gen. Chem. USSR 34 (1964) 3425; (3) A. Storr, K.Jones and A. W. Laubengayer, J. Amer. Chem. Soc. 90 (1968) 3173; (4) G.B. Sakharovskaya, N. N. Korneev, A. F. Popov, S. Z. Snegova, A. F.Zhigach and M. V. Sobolewskii, Brit. 1, 319, 746 (Ch. CO8g) June 6,1973, Appl. 6621/71, March 11, 1971; (5) M. Aoyagi, T. Vada, Y. Tadokoroand S. Horikivi, Jpn. Kokai Tokkyo Kono 79, 64, 600 (Cl. CO8g 79/10) May24, 1979, Appl. 77/131,909 Nov. 1, 1977: (6) J. Herwig, Dissertation,Hamburg University (1979); (7) H. J. Vollmer, Dissertation, HamburgUniversity (1980); (8) A. Wolinska, J. Organomet. Chem. 234 (1982) 1;and M. Boleslawski and J. Serwatowski, J. Organomet. Chem. 254 (1983)159.

These methods bring the water and the aluminum alkyls into directcontact with each other. They are intended for the preparation of smallquantities for catalytic investigations. The methods of preparationdiffer with respect to the carrier for the water. Vandenberg (1) reactsaluminum alkyls and water without a carrier. Sakharovskaya et al. (4)use a N₂ stream as entrainer for the water required for the reaction. InHamburg the molecular-sieve method (6), (7) was developed. In thismethod, a molecular sieve loaded with water serves as carrier or sourceof water.

The direct method poses the risk of a slight "running away" of thereaction. The water, introduced into the reactor by means of a carrier,is bound to the latter only physically and therefore readily released,which renders a controlled reaction difficult.

When the water required for the partial hydrolysis of aluminum alkyls isintroduced chemically combined in the form of salt hydrates, slowliberation of the water of crystallization, and hence a quiet reaction,are assured. This reasoning has led to the water-of-crystallizationmethod, published by (10) G. A. Razuvajev, J. A. Sangolov, J. J.Nelkenbaum and K. S. Minsker, Jzw. Akad. Navk. SSR, Ser.Chim. 19 (1975)2547; (11) H. Hahnsen, Thesis, Hamburg University (1980); and (12) S. R.Rafikov, K. S. Minsker, J. A. Sangalov and J. J. Nelkenbaum, USSR Patent566,844, C. A. 87 (1977) 152373h.

Further methods of preparation are designed to obtain the Al-O-Allinkage through appropriate choice of organoaluminum compounds such asdialkylaluminum chloride and lithiumdialkyl aluminate, alkoxyaluminumdichloride or methylmethoxyaluminum chloride, and methylaluminumchloride or ethylaluminum chloride. These methods have been published by(13) H. Tani, T. Araki, N. Oguni, T. Aoyoagi and N. Ueyama, J. Pol. Sci.Po. Lett. (8) 4 (1966) 97; (14) H. Tani, T. Araki, N. Ogunbi, T. Aoyoagiand N. Ueyama, J. Amer. Chem. Soc. 89 (1967) 173; (15) N. Ueyama, T.Araki and H. Tani, Inorg. Chem. 12 (1973) 2218; (16) W. Kosinska, K.Zardecka, A. Kunicki, M. Boleslawski and S. Pasynkiewicz, J. Organomet.Chem. 153 (1978) 281; and (17) W. Kosinska, A. Kunicke, M. Boleslawskiand S. Pasynkiwicz, J. Organomet. Chem. 161 (1978) 289.

Aluminum oxanes can also be prepared by reacting aluminum trialkyls withPbO, as described by (18) M. Boleslawski and S. Pasynkiewicz, J.Organomet. Chem. 43 (1972) 81.

Lastly, the water-of crystallization method was improved by the use ofpredehydrated aluminum sulfate as a source of water, as described by(21) H. H. Hahnsen, Dissertation, Hamburg University (1984) and (22)Kaminsky and Hahnsen, German published patent application OS 32 40 383.

However, predehydration is expensive, and any insoluble or sparinglysoluble aluminum oxane which may form remains undetected and isdiscarded with the crystal slurry. It is nearly impossible to establisha mass balance for the reaction.

Consequently, aluminum oxanes have not been readily available inmoderately large quantities up to now, and their structure has thereforenot been clarified, nor have fields of application been developed forthem.

The object of the present invention is to develop a process forproducing aluminum oxanes which can be carried out also on a commercialscale and can be expected to permit a reduction in the cost of catalystsystems based on aluminum oxanes, the development of rare-earth-alloyoxanes with specific aluminum contents, and the use of aluminum oxanesand aluminum-containing metal oxanes as catalyst supports and asstarting materials for specialty ceramics.

In the underlying efforts to master the direct reaction of an aluminumtrialkyl, preferably aluminum trimethyl, with water in an inert solventsuch as toluene, a number of surprising facts came to light:

(A) On a bright surface of ice immersed in a solution oftrimethylaluminum, an evolution of gas occurs that is more or lesspronounced as a function of temperature. It is found that directly onthe surface the temperature is higher than in the vicinity and at thecore. The reaction then either accelerates to the point of going out ofcontrol or comes to an end. The ice surface then has a dull appearance.

(B) When an ice surface on which the reaction has come to an end isscoured bright with a steel wire in some areas, an evolution of gas willagain occur there, and at moderately high temperatures even violent gaseruptions. However, the evolution of gas will subside quickly. Theprocess ca be repeated time and again at temperatures between 200 and250 K.

(C) When a sheet of ice on whose surface no further reaction has beenobserved in a solution of trimethylaluminum is broken in the solution,gas will evolve mainly at the fractures.

(D) When tiny lumps of ice are used, the gas bubbles which form, andwhich do not readily separate from the lumps of ice, will lift thelatter to the surface of the solution. They will collect in a layer offoam. There an insoluble material which envelops the lumps of ice willform. This is an aluminum oxane which contains less than a methyl groupper aluminum atom.

(E) If the alkylaluminum solution is recirculated by means of aglandless gear pump and a focused powerful jet is directed below thesurface of the solution onto the surface of the ice introduced, areaction evidently takes place at the point where the jet impinges: Theice becomes bright and sustains a depression.

The following teaching is arrived at on the basis of these facts:

(a) It is necessary to create a well-defined ice surface in a solutionof alkylaluminum and keep it reactive by erosive action.

(b) The reactive surface must be subjected to a sufficiently strongstream for aluminum oxane which formed to be carried away and not to beable to react with more water from the ice surface to form insolublelow-alkyl aluminum oxane.

(c) The formation of small ice particles which are carried by gasbubbles into the foam layer should be prevented, or then the circulationof the liquid should be directed so that the particles are drawn fromthe foam layer into the liquid.

(d) To prevent the formation of insoluble aluminum oxane, it isadvisable to use an excess of alkyl (based on the available water).

(e) The gas evolution starting at the surface should nor be so strongthat the alkylaluminum solution is unable to constantly flood thesurface and remove the soluble reaction products. This may be controlledthrough the temperature of the surface and of the ice. It is thereforeadvisable to be able to control the temperature of the ice independentlyof the temperature of the surrounding trialkyl solution. This can beaccomplished within certain limits by placing the ice on a cooled dishin the solution and cooling the dish through a coolant loop of its own,another coolant loop being provided for holding the solution at thedesired temperature.

The invention is broadly directed to a process for producing aluminumoxane by subjecting frozen water in a solution of trialkylaluminum inhydrocarbons to erosive action. In particular, the invention is aprocess for producing methylaluminum oxane which is characterized inthat frozen water in a solution of trimethylaluminum in hydrocarbons issubjected to erosive action which is exerted by mechanical action or byone or more intensive liquid jets of the reaction solution sweeping overthe surface of the frozen water.

The mechanical action is preferably exerted by means of rapidly rotatingimpact blades or of scouring and scraping tools on a surface of thefrozen water.

One embodiment of the process is characterized in that a 5 to 15%solution of trimethylaluminum in toluene or cumene is used as thesolution of trimethylaluminum in hydrocarbons.

Another embodiment of the process is characterized in that the velocityof erosion and/or the velocity of cooling are/is controlled so that aninternal temperature of 250 K. is not exceeded, that a temperature offrom 220 to 240 K. is preferably obtained, and that the temperature isnot below 190 K.

A further embodiment of the process is characterized in that thevelocity of erosion and/or the velocity of cooling are/is controlled sothat, at an internal temperature of less than 250 K., not more than 0.25mole of water per liter of solution is eroded and reacted per hour.

Still another embodiment of the process is characterized in that thequantities of water and of trimethylaluminum are sized so that at theend of the reaction, that is, after the frozen water has been used up orthe erosion action has ceased, unreacted trimethylaluminum is stillpresent, preferably in an amount of from 10 to 50 g per liter.

A further embodiment of the process is characterized in that the desiredexcess of trimethylaluminum is introduced initially and then maintainedby being replenished at a rate of which the trimethylaluminum isconsumed.

The implementation of this process is described by way of example in anumber of operating instructions in the examples. The latter demonstratethat the inventive operating procedure prevents the formation ofinsoluble aluminum oxanes almost completely and further permits theimmediate reuse of the unreacted alkylaluminum and of the solvent in thenext batch. In a series of batches, both the water, introduced in theform of ice, and the alkylaluminum are therefore converted 100%, withyields of over 90% soluble aluminum oxane and correspondingly littleinsoluble aluminum oxane. No byproducts are formed.

EXAMPLE 1

To a one-liter agitated glass autoclave which is equipped with atemperature-control jacket and whose cover is provided with a glandlessagitator with a magnetic clutch, a temperature sensor, closeablecharging openings and gas connections and can also be cooled, and onwhose agitator shaft a conventional impeller and, in addition, cutterblades from a kitchen blender are mounted (see FIG. 1), a solution of360 ml of toluene and 40 ml (corresponding to 400 millimoles) oftrimethylaluminum are charged under a protective gas (countercurrentargon). After cooling to -80° C., 3.76 g of ice, cooled to -80° , isthrown in.

The charging opening is then closed and the connection to the gasmeasuring and collecting system is opened through a valve. Then theagitator is started and the agitating speed is increased until the iceadded is chopped. After a slight gas-evolution surge, the reaction setsin with a rate of gas evolution of from 1 to 2 liters per hour. As soonas the gas-evolution rate drops, the speed of rotation is increased andthe temperature raised by regulating the thermostat controlling thecooling jacket.

After from 8 to 9 liters of gas have been collected at room temperature,the thermostat is turned off. The temperature is then allowed to rise toroom temperature. A total of from 9.5 to 10 liters is collected at roomtemperature. This is the theoretical quantity for the reaction of 3.76ml of water with an excess of trimethylaluminum. The nearly colorlesssolution obtained is forced through a G4 sintered filter from theautoclave into a receiver, degassed, and freed from excesstrimethylaluminum and toluene by condensation in a high vacuum.

There remain from 16 to 17 g of a spongy, glassy material that can becrushed to a white powder. This material ignites spontaneously in airand dissolves readily in benzene, toluene and cumene as well as in otheraromatic compounds, sparingly in methylcyclopentane andmethylcyclohexane, and hardly at all in alkanes.

EXAMPLE 2

The agitated autoclave mentioned in Example 1 is suspended in the coldbath. In the interior of the autoclave, a temperature lower than -60° C.is obtained. Solvent, and trimethylaluminum in the solvent, are thencarefully charged in such a way that nearly pure solvent overlies arelatively concentrated solution at the bottom of the autoclave. Withthe agitator upright, the necessary ice is added to the liquid, theautoclave is closed, and the connection to the gas-measuring andgas-collecting system is established.

Low-speed agitation is now started, which causes the sudden initiationof the reaction. From a batch with 40 ml of trimethylaluminum, 360 ml oftoluene and 3.76 g of ice, up to 5 liters of methane per hour aregenerated, which can just barely be controlled. However, so much foammay form that reaction mass is forced out through the gas dischargeline. A receiver capable of being cooled should therefore be interposedbetween the autoclave and the gas-collecting vessel.

As soon as the gas-evolution rate drops, the speed of agitation isincreased so that erosion and size reduction of the ice particles setin. The speed of agitation is increased at intervals so that foaming canjust be controlled, which is the case at a gas-evolution rate of from 3to 4 liters per hour. When the agitation speed cannot be increasedfurther and the gas-evolution rate markedly decreases (at which pointabout 8 liters of gas will have been generated; if less has beengenerated, extra care is indicated), the temperature is allowed to riseto room temperature over a period of from one and one-half to two hoursby withdrawing the liquid coolant but agitating vigorously, with thereaction then going to completion. The spent solution is forced througha G4 sintered filter into a receiver.

On the filter there are from 2 to 3 g of a substance which is insolublein aromatic compounds and has an aluminum/methyl ratio of between 1 and2. The filtrate is treated as in Example 1 and yields approximately 12 gof methylaluminum oxane soluble in aromatics.

EXAMPLE 3 (Comparative Example)

To a one-liter three-necked flask, 360 ml of absolute (anhydrous) cumeneand 40 ml of pure trimethylaluminum are charged. The flask is equippedwith a KPG agitator , a protective-gas inlet and a gas outlet as well asa temperature-controlled dropping funnel. The three-necked flask iscooled to -40° C. by immersion in a cold bath.

In a separate vessel, 4 ml of water is suspended as finely as possiblein 50 ml of cumene by means of an Ultra-Turrex agitator while beingcooled to -30° C. Tiny and very thin lamellar ice crystals are soobtained which settle at a temperature above -30° C. and float at atemperature below -30° C. The suspension is transferred to the droppingfunnel, brought to a temperature of -20° C., and added in small portionsto the previously introduced alkyl. The reaction sets in immediately andmethane and a fine foam are formed along with small amounts of a whitesolid (insoluble aluminum oxane).

If foam formation becomes too violent or the rate of gas evolutionexceed 0.3 liters per minute with such a batch, the rate of reaction isreduced by immersing the three-necked flask for a short time in the coldbath beneath it. Within one hour, all water in the form of thesuspension has been added and about 10 liters of gas have beengenerated. At that point, the temperature in the flask should be about-20° C. Over a period of one hour, the temperature is allowed to rise toroom temperature with evolution of a little gas.

When from 9 to 10 liters of gas have evolved in a controlled manner, aviolent reaction will occur only with gross carelessness. As thetemperature rises, the solution becomes perfectly clear and bright withslow agitation, and some insoluble aluminum oxane or also aluminum oxidesettles out. The batch is drawn off through a G4 sintered filter and thefiltrate is worked up to soluble aluminum oxane.

The filter cake amounts to from 3 to 6 g and with access of water or airis apt to decompose violently. From the filtrate, from 13 to 16 g ofcrude product is obtained which dissolves readily in toluene and whenused as a catalyst component for soluble Ziegler catalysts exhibits theusual activity. It contains minor amounts of free trimethylaluminum.

The mixture of cumene and excess trimethylaluminum can be used asstarting solution for a new batch, for which purpose it need only beenriched with trimethylaluminum to a content of 40 ml per 400 ml ofsolution.

EXAMPLE 4

A tubular reactor with an inside diameter of approximately 80 mm and acapacity of 2.5 liters which is equipped with a cooling jacket is closedwith a flange at the top and the bottom. From each flange an agitatorshaft with a magnetic clutch projects into the reactor. Thehemispherical lower mixing space is filled with cumene and is inexchange with the contents of the reactor only through the sealingclearance. A cooled annular plate is mounted on the lower flange in sucha way that the horizontally disposed annular plate surrounds thevertical agitator shaft so that the latter is able to move without beingencumbered by the annular plate.

After the reactor has been evacuated and filled with argon, water isintroduced into the depression in the annular plate and deep-frozen byturning on the cooling system of the annular plate. Onto the lowershaft, above the annular plate, a milling cutter is now placed which bymeans of a pin is guided in a slot in the agitator shaft. As theagitator shaft rotates, the milling cutter consequently exerts agrinding action on the surface of the deep-frozen ice, regardless of itsthickness.

The agitator shaft projecting from the upper flange, and thewall-scraping agitator mounted on it, serve to thoroughly mix the liquidcontent of the reactor and can be rotated and controlled independentlyof the lower agitator shaft.

The annular plate is now filled with 7.5 g of water and then cooled tofrom 205 to 210 K. The free ice surface obtained in this case measures41 cm², due to the construction.

On completion of the freezing of the water, 800 ml of precooled toluene(or cumene) is introduced. The liquid level is about 10 cm above theagitator plate. The wall-scraping agitator on the upper shaft dips intothe liquid. By charging the cooling jacket, the introduced liquid isalso cooled to 210 K. To the cooled liquid there is now added 80 ml,corresponding to 60 g, of trimethylaluminum, a portion of whichdissolves while another portion freezes out and overlies the liquid as acrystal slurry. After providing for pressure equalization, establishinga connection to a gas meter through a blubber valve and buffer vessel,and introducing a thermoelement into the liquid, the cutter head isfirst set into motion through the lower agitator and then the dissolvedand suspended trimethylaluminum is dispersed in the inert liquid bymeans of the upper agitator.

At the annular plate, an evolution of tiny gas bubbles sets in. Byreducing the cooling, the temperature is allowed to rise to 220 to 230K., with the rate of gas evolution then reaching values of up to 12liters per hours. After three hours, 18 liters of gas have evolved.(Room temperature.) Over a period of another hour, the temperature isallowed to rise to room temperature, with a further 2 liters of gasbeing generated. Few flocs precipitate in the solution. The solution isforced into a glass flask under argon. The solvent is condensed offunder vacuum and after being replenished can be used along with anytrimethylaluminum present for the next batch without being worked upfurther. Residue: 27 g methylaluminum oxane with traces oftrimethylaluminum.

We claim:
 1. A process for producing methylaluminum oxane, whichcomprises subjecting frozen water in a solution of trimethylaluminum inhydrocarbons to erosive action exerted by mechanical action on thesurface of the frozen water or by one or more intensive liquid jets ofthe solution sweeping over the surface of the frozen water.
 2. A processas defined in claim 1, wherein said mechanical action is exerted byrapidly rotating impact blades.
 3. A process as defined in claim 1,wherein said erosion is effected by means of scouring and scraping toolson a surface of the frozen water.
 4. A process as defined in claim 1,wherein a 5 to 15% solution of trimethylaluminum in toluene or cumene isused as the solution of trimethylaluminum in hydrocarbons.
 5. A processas defined in claim 1, wherein the velocity of erosion, the velocity ofcooling or both are controlled so that an internal temperature fromabout 190 to 250 K. is obtained.
 6. A process as defined in claim 5,wherein the velocity of erosion, the velocity of cooling or both arecontrolled so that, at an internal temperature of less than 250 K., notmore than 0.25 mole of water per liter of solution is eroded and reactedper hour.
 7. A process for producing an aluminum oxane, which comprisessubjecting frozen water in a solution of trialkylaluminum inhydrocarbons to erosive action.
 8. A process as defined in claim 7,wherein said aluminum oxane is methylaluminum oxane.
 9. A process asdefined in claim 7, wherein said frozen water is in a solution oftrimethylaluminum in hydrocarbons.
 10. A process as defined in claim 7,wherein said erosion controls through mechanical action exerted on thefrozen water.
 11. A process as defined in claim 10, wherein saidmechanical action is exerted by rapidly rotating impact blades.
 12. Aprocess as defined in claim 10, wherein said erosion is effected bymeans of scouring and scraping tools on a surface of the frozen water.13. A process as defined in claim 7, wherein said erosion is effectedthrough one or more intensive liquid jets of the solution sweeping overthe surface of the frozen water.
 14. A process as defined in claim 9,wherein a 5 to 15 weight % of trimethylaluminum in toluene or cumene isused as the solution of trimethylaluminum in hydrocarbons.
 15. A processas defined in claim 7, wherein the velocity of erosion, the velocity ofcooling or both are controlled so that an internal temperature fromabout 190 to 250 K. is obtained.
 16. A process as defined in claim 15,wherein said temperature is from about 220 to 240 K.
 17. A process asdefined in claim 15, wherein the velocity of erosion, the velocity ofcooling or both are controlled so that, at an internal temperature ofless than about 250 K., not more than about 0.25 mole of water per literof solution is eroded and reacted per hour.
 18. A process as defined inclaim 9, wherein the quantities of water and of trimethylaluminum aresized so that after the frozen water has been used up or the erosiveaction has ceased, unreacted trimethyaluminum is still present.
 19. Aprocess as defined in claim 18, wherein said unreacted trimethylaluminumis present in an amount of about 10 to 50 g per liter.
 20. A process asdefined in claim 9, wherein an excess of trimethylaluminum is introducedinitially and then maintained by replenishment at a rate at which thetrimethylaluminum is consumed.